Question

我让我的项目有效，并决定为用户引入一个设置页面进行基本调整。

Entity name: "Setting"
Attribute: "settingTimeOverrideSlider"
-> I created the NSManagedObject Subclass

我添加了（并嵌入）了SettingsViewController，即segue，命名为segue。

在该页面上，我使用按钮保存更改。这个按钮在我的CoreViewController中通过[super saveAndDismiss]调用了一个方法，我知道它进入那里（用NSLog检查）。

以下是方法：

-(void)saveAndDismiss
{
    NSLog(@"In Save And Dismiss");
    NSError *error = nil;
    if ([self.managedObjectContext hasChanges]) {
        NSLog(@"In Save And Dismiss - has changes");
        if (![self.managedObjectContext save:&error]) {                 // save failed
            NSLog(@"Save failed: %@", [error localizedDescription]);
        } else {                                                        // save succeeded
            NSLog(@"Save Succeeded");
        }
    }
    [self dismissViewControllerAnimated:YES completion:nil];    
}

但由于某种原因，它永远不会进入第一个if()，我的下一个调试NSLog。

我相信我的问题是我的主页中的prepareForSegue，因为所有其他的segues都会转到tableViews。我不确定我的segue设置是否正确

-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(UITableViewCell*)sender
{
    // segues 1-3
    if ([[segue identifier]isEqualToString:@"segue4"])
    {
        // some other Segue
    }

    if ([[segue identifier]isEqualToString:@"toSettings"])
    {
        UINavigationController *settingsViewController = segue.destinationViewController;

        SettingsViewController *editSettingsViewController = (SettingsViewController*)settingsViewController.topViewController;

        NSIndexPath *indexPath = [self.fetchedResultsController objectAtIndexPath:0];

        Setting *editSettings = (Setting*)[self.fetchedResultsController objectAtIndexPath:indexPath];

        editSettingsViewController.editSetting = editSettings;
    }
}

在我的SettingsViewController.h中，我将我的SettingsViewController子类化为我的CoreViewController的一部分，如下所示：

// SettingsViewController.h
#import <UIKit/UIKit.h>
#import "Setting.h"
#import "CoreViewController.h"

@interface SettingsViewController : CoreViewController
@property (nonatomic, strong)Setting editSetting;

@property (nonatomic, strong)Setting *editSetting;
@property (strong, nonatomic) IBOutlet UIBarButtonItem *editSaveButton;
@property (strong, nonatomic) IBOutlet UITextField *timeOverrideTextlabel;
@property (strong, nonatomic) IBOutlet UISegmentedControl *timeFormatSelector;
@property (strong, nonatomic) IBOutlet UISwitch *timeOverrideSlider;

- (IBAction)cancel:(UIBarButtonItem *)sender;
- (IBAction)editSave:(UIBarButtonItem *)sender;
- (IBAction)timeOverride:(UISwitch *)sender;

现在，当我尝试从持久性内存中检索信息时，是否需要将上述语句更改为

@interface SettingsViewController : CoreViewController
    <NSFetchedResultsControllerDelegate>

//SettingsViewController.m
#import "SettingsViewController.h"
#import "AppDelegate.h"

@interface SettingsViewController ()

@property (nonatomic, strong)NSManagedObjectContext *managedObjectContext;
@property (nonatomic, strong)NSFetchedResultsController *fetchedResultsController;

似乎无法解决这里的错误，但我确定它在我的prepareForSegue方法中（如上所列）。

就像我说的那样，所有其他的segue if语句用于链接到TableViews并且工作正常。

我试图像这样设置我的属性

editSetting.settingTimeOverrideSlider = @YES;

然后我打电话

[super saveAndDismiss];


- (IBAction)editSave:(UIBarButtonItem *)sender
{
    if ([_editSaveButton.title isEqualToString:@"Edit"])
    {
        [self setTitle:@"Edit Settings"];

        _timeFormatSelector.userInteractionEnabled = YES;
        _timeOverrideSlider.userInteractionEnabled = YES;

        _editSaveButton.title = @"Save";
    } else if ([_editSaveButton.title isEqualToString:@"Save"])
    {
        [self setTitle:@"Settings"];

        NSLog(@"SAVING-SVC");
        editSetting.settingTimeOverrideSlider = @YES; // THIS IS WHAT SHOULD CHANGE IN CORE DATA
        [super saveAndDismiss];
    }
}

Answer 1

您不应将fetchedResultsController或managedObjectContext发送到SettingsViewController。您应该尽可能限制需要配置的信息量。您已经发送了editSetting，这足以获得您想要的结果。

在SettingsViewController中，删除以下两行：

@property (nonatomic, strong)NSManagedObjectContext *managedObjectContext;
@property (nonatomic, strong)NSFetchedResultsController *fetchedResultsController;

相反，您应该直接从NSManagedObject访问托管对象上下文。

您的saveAndDismiss现在应该是这样的：

-(void)saveAndDismiss
{
    NSLog(@"In Save And Dismiss");
    NSError *error = nil;
    if ([self.editSetting.managedObjectContext hasChanges]) {
        NSLog(@"In Save And Dismiss - has changes");
        if (![self.editSetting.managedObjectContext save:&error]) {                 // save failed
            NSLog(@"Save failed: %@", [error localizedDescription]);
        } else {                                                        // save succeeded
            NSLog(@"Save Succeeded");
        }
    }
    [self dismissViewControllerAnimated:YES completion:nil];    
}

注意self.managedObjectContext成为self.editSetting.managedObjectContext的方式。

更好的是，您可以将[self.editSetting.managedObjectContext hasChanges]更改为[self.editSetting isUpdated]。

核心数据与保存更改存在问题

1 个答案: